1. Field of the Invention
The present invention relates generally to the field of automated high-speed imaging systems, and more specifically to electro-optical inspection and metrology systems for semiconductor wafers and reticles.
2. Description of the Related Art
Semiconductor wafer and reticle inspection tools are constantly being improved to meet the growing challenges of inspecting smaller and smaller features. Rapid advancements in new device structures, materials, associated lithography techniques, and reticle enhancement strategies for developing circuits are dramatically increasing circuit complexity. Increased complexity resulting from smaller features in conjunction with the advancement in manufacturing materials and techniques impose increased demands and additional requirements on the semiconductor silicon wafer inspection process. In particular, the materials and techniques produce new defect types and noise sources, resulting in a dramatic rise in critical defects along with greater difficulty of detection.
To meet these demands, today's industrial inspection and metrology imaging systems enable the collection of more than one channel of information for both static imaging and high-speed scanning defect detection systems. The term “channel” or the like used herein means an imaging mode, including but not limited to: bright field and dark field imaging, large-signal/small-signal readout, multi-spectral imaging, transmitted/reflected simultaneous imaging, and broadband/narrow band optical imaging modes. Multiple mode inspection is becoming an industry wide necessity to ensure optimal detection of the broadest range of defect types.
As a result, manufacturers now produce inspection systems capable of supporting multiple configurations to affect a wide variety of imaging collection modes and are optimizing components for specific inspection applications, thus providing system solutions that collect more than one channel of information. For example, a wafer surface inspection system may use a dark field imaging mode to detect highly scattering particles such as dust on a smooth and uniform surface and a bright-field imaging mode to identify stains or other surface contamination.
Traditionally, wafer inspection systems have employed sensors such as time-delay-integration (TDI) sensors to inspect an object using die-to-die or die-to-database inspection techniques. Collecting more than one channel of information during the inspection process can be technically difficult, but particularly can be time consuming. Conducting multiple inspections, in conjunction with performing certain measurements, significantly increases the total required inspection time and expense.
Thus it would be advantageous to offer an inspection architecture and design employing a sensing device or devices, wherein the inspection design provides robust and reliable image collection, capable of use with multiple imaging modes, and overcomes the drawbacks associated with previous systems used to perform multiple mode inspections.